This invention relates to fuel control systems for gas turbine engines, and in particular, to a fuel control valve for proportioning fuel being supplied to the combustor of the turbine engine into a first portion for delivery to primary fuel nozzles and a second portion for delivery to secondary fuel nozzles.
FIG. 1 shows a prior art fuel control valve generally denoted by reference numeral 1. The fuel control valve 1 comprises a generally cylindrical, axially extending hogged out sleeve 2. The casing 2 has a first set of circumferentially spaced holes 3 and a second set of circumferentially spaced holes 4. Disposed within the casing 2 is a plate seal 5 having holes 6. The plate seal 5 has a hollow center and is coupled to valve 7. Disposed within the plate seal 5 and valve 7 is a piston 8 mounted on a spring 9. In operation fuel enters the inlet of 10 and flows through holes 3 and hole 6, pushing piston 8, then flowing out hole 4. As the fuel pressure builds within the interior, the piston moves and compresses the spring. Due to frictional engagement of the various parts, as the piston moves so does the valve 7 and the plate seal 5. A disadvantage to this prior art fuel control valve is that because of the frictional contact, hysterisis develops which makes the fuel flow from the valve unpredictable.
Accordingly, there is a need for a fuel control valve that overcomes this hysterisis problem.
An object of the present invention is to provide a fuel control valve that is not as susceptible to hysterisis as prior art valve.
The present invention achieves the above-stated objective by providing a fuel control valve for proportioning fuel being supplied to the combustor of the turbine engine into a first portion for delivery to primary fuel nozzles and a second portion for delivery to secondary fuel nozzles comprising:
an axially extending hollow casing having a first hole and a second hole axially spaced apart from said first hole, said first hole on fluid communication with said primary nozzles and said second hole in fluid communication with said secondary nozzles;
an annular metering block disposed within said casing, said metering block having a third hole in fluid communication with said first hole and a fourth hole in fluid communication with said second hole, said third and fourth hole being axially spaced from each other;
an annular bushing disposed in said casing adjacent said metering block to define a conduit extending through said casing from a first opening for receiving a flow of fuel and a second opening; and
a stop valve disposed in said second opening and having a piston mounted thereto, said piston slidingly engaging said bushing to be continuously operable between a first position where said piston covers said third and fourth holes and a second position where said third and fourth holes are not covered by said piston.
These and other objects, features and advantages of the present invention are specifically set forth in, or will become apparent from, the following detailed description of a preferred embodiment of the invention then read in conjunction with the accompanying drawings.